The present invention relates to machines for manipulating rod-shaped articles which constitute or form part of smokers' products. More particularly, the invention relates to machines wherein groups of two or more coaxial rod-shaped articles are connected to each other by adhesive-coated uniting bands which are convoluted around the respective groups while the groups move sideways through a gap whose width is less than the diameters of articles which form a group. Still more particularly, the invention relates to improvements in apparatus which form part of such machines and define the aforementioned gaps wherein groups of coaxial rod-shaped articles roll about their respective axes.
Filter cigarettes are normally produced in machines wherein two plain cigarettes of unit length are connected with a filter plug of double unit length by means of an adhesive-coated uniting band which is draped around the filter plug and the adjacent end portions of the plain cigarettes. The resulting filter cigarette of double unit length is thereupon severed midway between its ends to yield a pair of filter cigarettes of unit length. The draping of uniting bands takes place while the plain cigarettes and the respective filter plugs are caused to move sideways between the peripheral surface of a rotary drum-shaped draping conveyor and a stationary rolling device. As a rule, the rolling device is heated to promote the setting of adhesive which is applied to those sides of the uniting bands that contact the respective filter plugs and the inner end portions of corresponding plain cigarettes. Such heating presents problems when the filter plugs contain or consist of a filter material which is sensitive to heat. For example, the so-called NWA-filters (namely, non-wrapped-acetate filters) are likely to adhere to the rolling device and/or to the draping conveyor during prolonged dwell in the gap between the conveyor and the rolling device. This can happen when the machine is arrested, e.g., due to a malfunction of one of its units.
The uniting bands which are located in the gap between the rolling device and the draping conveyor are in different stages of conversion into tubular envelopes, i.e., at least some of the filter plugs are exposed and, therefore, such filter plugs are even more likely to adhere to the heated surface of the rolling device. This can entail a lengthy interruption of operation in order to remove molten material from the rolling device and/or from the periphery of the draping conveyor. Each interruption is extremely costly because a modern filter cigarette making machine turns out a minimum of seventy articles per second. NWA-filters normally contain a solvent, such as triacetin, which bonds portions of filaments to each other in order to provide a maze of passages for tobacco smoke and to thus insure interception of high percentages of tar and nicotine while the smoke flows toward the smoker's mouth. Triacetin melts in response to heating and flows onto the adjacent surfaces of the rolling device and/or draping conveyor when a filter of such type is compelled to remain in the gap for a relatively long period of time. As mentioned above, NWA-filters are unwrapped, i.e., their peripheral layers are merely reinforced as a result of suitable thermal or chemical treatment whereby such reinforced layers constitute porous envelopes. Therefore, when a porous envelope is permitted to directly contact the heated rolling device while the draping conveyor is idle, the filter undergoes partial disintegration and contaminates the adjacent parts of the machine.